Step 1: Measure Roomba

If you're being careful, use a measuring tape to get the diameter of your Roomba at its widest, and the height of your Roomba at its tallest. That way, your patterns are less seat-of-the-pants. I was not so careful, and just traced the patterns directly from the Roomba.

Step 2: Make patterns

The pdf file with the pattern for the mouse pieces is the guide for all following steps. It's not at all to size, but it is roughly to scale. Based on the measurements of your own Roomba, use it as a guide. You may want to enlarge each shape to the exact size on a copier, or just roughly copy the shapes onto scrap paper. The brown paper from cut-up paper grocery bags is ideal because it won't mark up whatever fabric you're using (unlike newsprint).

When I was making the mouse, I didn't bother with making patterns for the top and sides at all - I just drew and cut directly from the Roomba itself (see Step 3).

Cut whatever pieces you've made out of whatever kind of paper you're using.

My girlfriend already thinks the stock roomba is cute in its mousy movement... and calls it "Roomba" in the first person. I can't put a costume like this on it or it'll be too cute! Also, I was wondering if you covered the vacuum exhaust or if you left an undocumented hole for it? Wouldn't want people to cover that up...